Stabilization of hydrocarbon distillates



drums, tanks, etc.

United States Patent 2,844,44 Patented July 22, 1958 STABILIZATION orHYDROCARBON. f

No Drawing. Application February 2,1956 Serial No. 562,939

' sclaims. "(CL 44-63 This application is a continuation-impart of ourco pending application Serial No. 478,488, filed December 29, 1954, nowabandoned, and relates to a novel process for the stabilizationof-hydrocarbon distillates.

' As will be shown by the examples appended to the presentspecifications, the novel process of the present invention serves toimprove hydrocarbon distillates in a number of important ways. Forexample, in fuel oil, burner'oil, range oil, diesel oil, marine oil,turbine oil, cutting oil, rolling oil, drawing oil, slushing oil,lubricating oil, etc., the oil is improved in one or more ways includingretarding and/ or preventing sediment formation, dispersion of sedimentwhen formed, preventing and/or retarding discoloration, oxidationinhibitor, rust or corro sion preventative, detergent properties, etc.In lubricating type oils, in addition to some of the other propertieshereinbefore setforth, the additive may function as a pour pointdepressant, viscosity index improver, antifoaming agent, extremepressure additive, oilness additive, etc. In gasoline, naphtha, aromaticsolvents, kerosene, jet fuels, etc., 'the additive serves as a corrosioninhibitor, along grees.

The hydrocarbon distillate may be cracked, straight run or mixturesthereof. Many fuel oils and particularly blends of straight run andcracked fuel oils undergo deterioration in storage resulting in theformation of sediment, discoloration, etc. The formation of sediment isobjectionable because the sediment tends to plug burner tips, injectors,etc. In diesel fuel, the deterioration tends,

to: form varnish and sludge in the diesel engine. Dis coloration of fueloils is objectionable for various reasons, including customerspreference for light colored oils.

In the handling of hydrocarbon distillates, it is often.

necessary to transport and/or store such materials in metal containers,as in steel or other metal pipe lines, Since these. materials oftencontain varying amounts of water in solution or in suspension which mayseparate, due to temperature changes, internal 5 corrosion of thecontainer by separating water almost invariably occurs to a greateror'lesser degree. The water thus separated forms as a film or'in minutedroplets in the pipe line or on the container walls or even in smallpools at the bottom of the container. This brings about ideal conditionsfor corrosion and consequent damage to the metal surfaces of thecontainer, as well as the serious I contamination of the hydrocarbon oilcontained therein'by the corrosion products.

Corrosion problems also occur, for example, in the lubrication ofinternal combustion engines or steam en- 'gines, including turbines andother similar machinery, in

which quantities of Water are often observed as a separate phase withinthe lubricating system as a result of the condensation of water from theatmosphere or, in the case of internal combustion engines, as the resultof dispersion or absorption in lubricating oil of Water formed as aproduct of fuel combustion. Water in such instances corrodes the variousmetal parts of the machinery with with the other functions mentionedabove to various de-,

the reaction temperature and slow the reaction,

which it comes into contact, the corrosion products cans ing furthermechanical damage to bearing surfaces and the like due to their abrasivenature and catalytically promoting the chemical degradation of thelubricant.

In one embodiment the present invention relates to 'a process forstabilizing a hydrocarbon distillate which comprises incorporatingtherein a stabilizing concentration of a bis-tetrahydropyrimidine joinedat the 2-position through a divalent hydrocarbon radical.

In a specific embodiment the present invention relates to a process forstabilizing fuel oil which comprises incorporating therein a stabilizingconcentration of a bistetrahydropy-rimidine joined at the 2-positionthrough a divalent hydrocarbon radical. e

The bis-tetrahydropyrirnidines for use in accordance with the presentinvention may be illustrated by the fol lowing general formula.

where R is a hydrocarbon radical containing at least 2 carbon atoms andR is hydrogen, a hydrocarbon or a substituted hydrocarbon radical. Itwill be noted that the bis-tetrahydropyrimidines for use in the presentinvention are joined together through thel2-position. p i

.The specific composition of the R radical will depend upon theparticular polycarboxylic acid utilized in preparing the.bis-tetrahydropyrimidine as hereinafterwill be described in. detail.Similarly, the specific composition of the'R' radicals will depend uponthe particular alkylene polyamine utilized in preparing the compound, aswell as the furtherreaction thereof, both of which will be furtherdescribed in detail herein.

The bis-tetrahydropyrimidines for use in the present invention areprepared by the condensation, with the formation of 4 molecules'ofwater, of 2 mols of an alkylene polyamine having at least 1 primaryamino group separated from another primary or secondary amino group by 3carbon atoms, withl mol of a dicarboxylic acid. This reaction generallyis effected at a temperature above about F., and preferably at a highertemperature which usually will not exceed about 350, to 400 F. Ashereinbefore mentioned, Water is formed during the reaction and, tofacilitate the removal thereof and to effect more complete reaction, ahydrocarbon solvent, preferablyone 'whichformsan azeotropic mix turewith water, may be utilized. Preferred solvents comprise aromatichydrocarbons including benzene, toluene, xylene, cumene, naphtha, etc.Any suitable amount of solvent may be employed and preferably should notcomprise a large excess because this will tend to lower In anotherembodiment, removal of the water may be facilitated by operating under areduced pressure. In still another embodiment, the water of reactionmaybe removed by distillation of the reaction product at elevated tem-.

perature.

As hereinbefore set forth, the specific compositions 3 of R and R in theabove general formula will depend upon the particular reactantsutilized. For example, the condensation of 2 mols of3,3-imino-bis-propylamine with 1 mol of succinic acid, with theformation of 4 molecules of water, produces a bis-tetrahydropyrimidineof the following formula:

The above reaction and product are typical illustrations of the additivecompounds for use in the present invention and the method of preparationthereof. The same general reaction is elfected utilizing other alkylenepolyamines having at least 1 primary amino group separated from anotherprimary or secondary amino group by 3 carbon atoms.

The following are mentioned as representative of suitable alkylenepolyamines for use in preparing the additive: 1,3-propylene diamine,-dipropylene triamine, 1,3- diaminobutane, 2,4-diaminopentane,N-ethyl-trimethylene diamine, N-aminoethyl-trimethylene diamine,aminopropyl-stearylamine, tripropylene-tetramine,tetrapropylene-pentamine, 3,3-imino-bis-propylamine, higher boilingpolyamines prepared by the condensation of 1,3-propylene dichloride withammonia, other polyamines in which at least 1 primary amino group isseparated from another primary or secondary amino group by 3 carbonatoms, and mixtures of alkylene polyamines.

For the purpose to be hereinafter set forth in detail,3,3-imino-bis-propylamine is a preferred alkylene polyamine for use inthe preparation of the bis-tertahydropyrimidines. However, for economicreasons, in some cases, it may be desirable to utilize certainsubstituted propylene polyamines which are recovered, usualy as amixture of compounds, as a by-product in the manufacture of certain purecompounds or which may be prepared from a mixture of reactants availableat a lower cost. In many cases, the final products formed from themixture will be satisfactory for the desired use and, therefore, can beprepared at a much lower cost. It is understood that thebis-tetrahydro-pyrimidine so produced may comprise a mixture ofbis-terta-hydropyrimidines and also that the product may contain othercomponents. Examples of such a mixture available commercially are alkylpropylene diamines in which the alkyl group is derived from tallow,lauric acid, cotton seed and soya, these being available under the tradenames of Duomeen-T. Duomeen-IZ, Duomeen-C, and Duomeen- S, respectively.Duomeen-T is particularly preferred and is believed to contain fromabout 12 to about 20 carbon atoms per alkyl group, mostly 16 to 18carbon atoms, and has a theoretical molecular weight of 320 and acombining molecular weight (based on 80% active ingredient) of about400. It is a soft paste and has a melting range of from 111 to 118 F.

Any suitable polycarboxylic acid may be utilized in preparing thebistetrahydropyrimidines. Polycarboxylic acids include oxalic, malonic,succinic, glutaric, itaconic, mesaconic, citraconic, adipic, pimelic,suberic, a'zelaic, sebacic, phthalic, aconitic, citric, hemimellitic,trimellitic,

trimesic, prehnitic, mellophanic, pyromellitic, mellitic, etc., higherpolybasic carboxylic acids, and mixtures thereof.

Here again, for economic reasons, it may be preferred to use adicarboxylic acid product available commercialy at lower cost andpreferably containing from about 10 to about 50 carbon atoms permolecule. An example of such an acid is available as dimer acid(dilinoleic acid), which is liquid at 77 F., and is said to have an acidnumber of l80192, an iodine number of 80-95 and a dimer content of aboutAnother example of a byproduct acid is one being marketed commerciallyunder the trade name of VR-l Acid. This acid is a liquid at 77 F., andis stated to have an acid number of about 150, an iodine number of about36 and average molecular weight of about 1000. It is believed that thisacid contains about 30 to 40 carbon atoms per molecule. When such anacid is used in preparing the bis-tetrahydropyrimidines, it isunderstood that the reaction product will contain a mixture thereof.

As hereinbefore set forth, the reaction of the alkylene polyamine withthe polycarboxylic. acid generally is effected at a temperature withinthe range of about to about 400 F., although higher or lowertemperatures may be employed under certain conditions. The exacttemperature will depend upon whether a solvent is used and, whenemployed, on the particular solvent. For example, with benzene as thesolvent, the temperature will be of the order of 176 F., with toluenethe temperature in the. order of 248 F. and with xylene the temperaturein the order of 297 F. When no solvent is employed, the temperature willbe sufiicient to remove the water formed in the reaction. The reactionmay be continued until it goes to completion, which may be determined bymeasuring the amount of water evolved which, as hereinbefore set forth,will comprise 4 molecules of water per mol of dicarboxylic acid.However, for many purposes, as will be hereinafter described, thereaction need not go to completion. In any event, at least a substantialportion of the reactionproduct will comprise a bis-tetrahydropyrimidinehaving the configuration hereinbefore set forth. The water formed in thereaction may be removed in the manner hereinbefore described and theresultant product is recovered as a viscous liquid in most cases. Insome cases, the bis-tetrahydropyrimidine will be utilized as a solutionin a solvent. Conveniently, this solvent comprises the same solventutilized in preparing the bistetrahydropyrimidine and advantageously isrecovered in admixture with at least a portion of the solvent, therebyavoiding the necessity of removing all of the solvent and subsequentlyadding it back. When a more dilute solutionis desired than is recoveredin the manner hereinbefore set forth, it is understood that the same ordifferent solvent may be commingled with the mixture to form a solutionof the desired concentration.

It is understood that the bis-tetrahydropyrimidines for use in thepresent invention may contain substituents replacing one or all of thehydrogen atoms attached to the carbon atoms in the 4, 5, 6, 4', 5' and6' positions, as well as replacing hydrogens attached to the carbonatoms in the side chains. The substituents may be hydrocarbon orsubstituted hydrocarbon groups, the latter including those containingoxygen, nitrogen, phosphorus, sulfur, halogen, etc. These substituentsmay inherently be present clue to the specific reactants employed inpreparing the bistetrahydropyrimidine or they may be added by asubsequent condensation reaction.

In another embodiment of the invention, the additive comprises an amideformed by reacting the bis-tetrahydropyrimidine having a side chaincontaining a primary or secondary amino group with a carboxylic acid,with the evolution of 2 molecules of water. For example, the histetrahydropyrimidine formed by the condensation of 2 mols of3,3'-imino-bis-propylamine with 1 mol of sucetc.

The above reaction and product are typical illustrations of one additivefor use in the present invention. The formation of the amide is effectedunder substantially the same conditions as hereinbefore set forth forthe preparation of the bis-tetrahydropyrimidines. However, when the sidechain contains more than one primary and/or secondary amino groups, itis desirable to use a lower temperature, preferably below about 215 F.,in order to avoid forming additional pyrimidine or otherrings.

Any suitable monocarboxylic acid may be utilized in preparing the amide.The monocarboxylic acid preferably is selected with reference to theparticular bistetrahydropyrimidine and the purpose for which the finalcompound is to be used. For example, where increased solubility. in aparticular hydrocarbon distillate is desired, it generally is preferredto utilize a comparatively long chain monocarboxylic acid. Particularlypreferred monocarboxylic acids for use in the preparation of an amide,which in turn is to be utilized as an additive to hydrocarbondistillates, include fatty acids and particularly oleic acid, linoleicacid, palmitic acid, stearic acid, etc. Other monocarboxylic acidsinclude formic, acetic, propionic, butyric, valeric, trimethylacetic,caproic, theptylic, caprylic, pelargonic capric, lauric, myristic,arachidic, behenic, lignoceric, cerotic, etc., decylenic, dodecylenic,palrnitoleic, ricinoleic, petroselinic, vaccenic, linolenic,eleostearic, licanic, parinaric, gadoleic,

arachidonic, cetoleic, erucic, selacholeic, etc., and mixtures thereof.1

In some cases, the monocarboxylic acid may contain hydroxy substituentsas, for example, in acids as glycolic, lactic, hydroxybutyric, etc. Inother cases, the monocarboxylic acid may contain other substituentsattached thereto, which sub'stituents may be hydrocarbon or substitutedhydrocarbon groups, the latter including those containing oxygen,nitrogen, phosphorus, sulfur, halogen,

In another embodiment, a mixture of monocarboxylic acids may beemployed. As hereinbefore set forth, the above acids are recited merelyfor illustrative purposes and are not intended to be limiting. Theparticular acid will be selected on the basis of the particularhydrocarbon distillate in which the additive is to be incorpo-- rated.It is understood that the various amides formed in the mannerhereinbefore set forth will not necessarily be equivalent.

. As an example of a modification of the amide comprised within thescope of the present invention, a histetrahydropyrimidine having aprimary amino group in the side chain may be reacted with an aldehyde orketone in the presence of hydrogen, and the resultant secondary. aminogroups utilized to form the amide by reaction with the monocarboxylicacid.

' While the amide formed from the monocarboxylic acid generallyispreferred, it is understood that amide formed in accordance with thepresent invention. 'The polycarfrom polycarboxylic acids may be preparedand utilized I boxylic acid may be selected from those hereinbefo're setforth in connectionwith the preparation of the bis-tetrahydropyrimidine.I

In still another embodiment, the additive for use in the presentinvention comprises a carboxylic acid salt of thebis-tetrahydropyrimidine or of the amide thereof. The salt may be anacid, basic or neutral salt, depending upon the amount of carboxylicacid utilized in preparing the salt. The neutral salt is prepared byutilizing stoichiometric amounts of the acid and amino groups. Each ofthe pyrimidine rings has a basicity equivalnt to one amino group.Therefore, the amino groups, which are computed in determining theamount of carboxylic acid, will be 2 aminogroups forthe'bis-tetrahydropyrimidine and 1 each for the primary and'secondaryamino groups in the side chains. In preparing the neutral salt, theconcentration of carboxylic acid and amine groups will be selected sothat there will be an equivalent number of carboxylic acid groups andamino groups. Thus, the specific concentrations will depend upon whetherthe acid is monobasic, dibasic, tribasic or higher polybasic acid, andon the number of amino groups as hereinbefore set forth. In anotherembodimennthe salt may be a basic, salt, which is prepared by utilizinga deficiency of carboxylic acid groups in relation to the amino groupsas, for example, by utiliing' 1 equivalent of carboxylic acid per 2equivalents of amino groups.

pared by using an excess of acid with relation to the amino group as,for example, 2 equivalents of acid per 1 equivalent of amino group. -Itis understood that these different salts are not necessarily equivalent.

When-a monocarboxylic acid is utilized in preparing the salt, it may beselectedfrom the monocarboxylic acids specifically set forthhereinbefore. Similarly, when a polycarboxylic acid is utilized informing the salt, it may be selected from those hereinbefore set forthin connection with the preparation of the tetrahydropyrimidine.Advantageously, the dicarboxylic acid utilized in preparing the bistetrahydropyrimidine may be employed in preparing the salt. In anotherpreferred embodiment, the monocarboxylic acid utilized in forming theamide is advantageously utilized in preparing the salt. It is understoodthat the-amide and/ or salt may be prepared simultaneously with thepreparation of thebis-tetrahydropyrimidine or the salt preparedsimultaneously with the preparation of the amide. This may beaccomplished by utilizing a sufficient excess of the carboxylic acid inorder to form the desired product. Inaddition to the formation of theamide'and/ or salt, in some cases there is evidence of the formation ofa complex between the amine and acid, which complex as yet has not beencompletely identified. It is understood that the novelcomposition ofbis-tetrahydropyrimidine, amide and/or salt also may I contain thecomplex.

The salt may be prepared in any suitable manner. It

In still another embodiment, an acid salt may be employed, which may bepre-- vigorous stirring. The salt is prepared readily at roomtemperature, although slightly elevated temperatures which generallywill not exceed about 200 F. may be employed when desired. Excessivetemperatures should be avoided in order not to form amides or additionalrings When not desired. In some cases, it may be desirable to utilize asolvent during the formation of the salt and, as hereinbefore set forth,the solvent advantageously is the same as that utilized in forming thefinal solution of the product.

It is understood that the various additives which may be prepared andused in accordance with the present invention are not necessarilyequivalent in the same or different hydrocarbon distillates. As anexample, a bistetrahydropyrimidine, amide or salt may be more effectivein one fuel oil, while another bis-tetrahydropyrirnidine, amide or saltmay be more effective in a ditferent fuel oil. Furthermore, theparticular bis-tetrahydropyrimidine, amide or salt to be used willdepend upon the specific benefits desired in the particular hydrocarbondistillate being treated.

As hereinbefore set forth, the particular additive will be selected onthe basis of the purpose which it is to serve and also on the specifichydrocarbon distillate in which it is to be used. In the case whereincreased solubility is desired in the hydrocarbon distillate, anadditive containing a higher number of carbon atoms is generallypreferred, the larger number of carbon atoms may be obtained by ajudicious selection of the amine and/or acid utilized in preparing thebis-tetrahydropyrimidine, in the selection of a long chainmonocarboxylic acid in forming the amide, and/or in the use of a saltprepared from a long chain carboxylic acid. Where increased corrosionprevention is desired, it generally is preferred to use an acid salt ofthe bis-tetrahydropyrimidine or amide. The concentration of additive tobe used likewise will depend upon the particular hydrocarbon distillateand the particular benefits desired. In general, the additive is used ina concentration of from about 0.0000l% to about by weight or more andgenerally in a concentration of from about 0.000l% to about 1% by weightof the hydrocarbon distillate. The additive may be used along with otheradditives which are incorporated in a hydrocarbon distillate forspecific purposes including, for example, metal deactivators,antioxidant, synergists, dyes, fuel irnprovers, etc.

The additive is incorporated in the hydrocarbon distillate in anysuitable manner. As hereinbefore set forth, the additive conveniently isutilized as a solution in a suitable solvent including hydrocarbons andparticular aromatic hydrocarbons as benzene, toluene, xylene, cumene,etc. The additive is readily incorporated in the hydrocarbon distillateby adding it in the desired amount to the distillate and suitableagitating or otherwise mixing in order to obtain intimate admixing ofthe additive and the distillate. When the additive is to be utilized asa corrosion inhibitor in plant equipment, it may be intro duced into afractionator, vapor line or at any other suitable point in order toprevent corrosion of the plant equipment. In this embodiment, theadditive carries over into the product of the process and also servestherein as a beneficient. It is understood that a portion of theadditive may be introduced into the plant equipment and an additionalportion of the additive added to the effluent product when so desired.

The following examples are introduced to illustrate further the noveltyand utility of the present invention but not with the intention ofunduly limiting the same.

EXAMPLE I In this example the additive was utilized in a catalyticallycracked cycle stock which is marketed as a fuel oil. The beneficialefiects obtained by the use of the additive are determined by means of anumber of different methods. In one method a sample of the fuel oil itWithout additive is stored at F. for 6 months or longer, and the amountof sediment formed during such storage, as well as thecolor of the oil,is determined. At the same time, another sample of the same oilcontaining an additive is stored under the same conditions and thesediment and color also are determined.

In another method of analysis, after storage at about 100 F. thedifferent samples of the oil are passed through a 400 mesh wire screenand the time in seconds for successive 300 cc. portions of the oil topass through the screen is recorded. This method analyzes the differentsamples as regards the property thereof to clog burner screen in actualservice. As hereinbefore mentioned, clogging of burner screens isobjectionable because it prevents satisfactory use of the fuel oil.

The colors of the different samples were determined in a Lumetron, Model402,E spectrophotometer. Distilled water is rated as 100. A very darkoil would be rated as 0 in this analysis.

The additive used in this example is a bis-tetrahydropyrimidine and wasprepared by reacting 2 mols of Duomeen-T with 1 mol of Dimer acid. Theproperties of Duomeen-T are set forth hereinbefore. The Dimer acid isdilinoleic acid and the properties thereof likewise are set forthhereinbefore. The Duorneen-T and Dimer acid were commingled with xyleneas the solvent, and the mixture was refluxed at a temperature of about300 F. for a period of about 6 hours. 4 molecules of water were evolvedper mol of acid. The product is a viscous medium brown liquid having anindex of refraction of 1.4907. Infrared spectrum showed a C=N band. Itcannot be distilled without decomposition.

0.005% by Weight of the bis-tetrahydropyrimidine prepared in the abovemanner was incorporated in a sample of the catalytic fuel oil, and theproperties thereof after storage in the manner hereinbefore set forthare reported below. Similar properties of another sample of the fuel oilnot containing the additive also are reported in the table.

Before storage in the manner hereinbefore set forth, the sample of oilwas free from sediment and had a color of 94. It will be noted that theadditive served to benefit the oil in reducing the sediment after about200 days of storage from 14 to 3.8 mg./l00 ml. and to have a final colorof 35 as compared to 20 for the control sample. Also, in the screentest, the sample without additive required over 200 seconds to passthrough the screen, thus indicating plugging of the screen, whereas thesample containing the additive passed through the screen in 10-14seconds.

EXAMPLE II 3,3'-imino-bis-propylamine was reductively alkylated withethylamyl ketone to form N-octyl-3,3'-imino-bispropylamine. TheN-octyl-3,3'-imino-bis-propylamine, dilinoleic acid and xylene wererefluxed at 300-3l0 F. for about 6 hours, with the evolution of 4molecules of water per mol of acid. The product was a light brownviscous liquid having an index of refraction of 1.4970. The productcould not be distilled without decomposition. The calculated molcombining weight is 281.5. Actual combining weight was 298.

0.01% of the bis-tetrahydropyrimidine was incorporated in acatalytically cracked fuel oil and exposed to air 9 at 212 F. for 20hrs. The oil after this exposure had a color of 73.3. A control sampleof the oil not containing additive had a color of about 11 after similarexposure.

EXAMPLE III A bis-amide of bis-tetrahydropyrimidine was prepared asfollows: 3,3-imino-bis-propylamine, sebacic acid and xylene wererefluxed at 300-310 F. for about 6 hours. Subsequently, 2 mols of oleicacid per mol of bis-tetrahydropyrimidine and xylene were added, and themixture refluxed at 300-310 F. for about 7 hours, with the separation of2 molecules of water per mol of bis-tetrahydropyrimidine. The bis-amidewas converted to the oleic acid salt with an index of refraction of1.4907. It could not be distilled without decomposition. The bis-amideas prepared in the above manner in incorporated in a commercial fuel oilin a concentration of 0.01% to reduce sediment formation therein and toimprove the color of the oil during storage.

EXAMPLE IV tion of 1.4838. Calculated mol combining weight is 878.5.Actual was 853.

When incorporated in another sample of the catalytically cracked fueloil and exposed as described in Example III, the fuel oil had a color of81.3 as compared to about 11 for the control sample.

EXAMPLE V pounds per 1000 pounds of oil of the acid salt of VR-1 Acidand the bis-tetrahydropyrimidine prepared fromN-octyl-3,3'-imino-bis-propylamine and VR-l Acid are injected into thevapor line of fractionating column in a cracking plant. This will serveto keep the I in storage containing a bis-tetrahydropyrimidine joined atthe 2-position through a divalent hydrocarbon radical, said compoundhaving the property of and being present in sufficient amount to retardsaid sediment formation.

3. Fuel oil normally susceptible to sediment formation in storagecontaining an amide of a bis-tetrahydropyrimidine joined at the2-position through a divalent hydrocarbon radical, said compound havingthe property of and being present in suflicient amount to retard saidsediment formation.

4. Fuel oil normally susceptible to sediment formation in storagecontaining a salt of a bis-tetrahydropyrimidine joined at the2-position-through a divalent hydrocarbon radical, said compound havingthe property of and being present in sufiicient amount to retard saidsediment formation.

5. Fuel oil normally susceptible to sediment formation in storagecontaining an acid salt of a bis-tetrahydropyrimidine joined .at the2-position through a divalent'hydrocarbon radical, said compound havingthe property of and being present in sufficient amount to retard saidsediment formation.

References Cited in the file of this patent UNITED STATES PATENTS2,194,419 Chwala Mar. 19, 1940 2,622,018 White et al. Dec. 16, 19522,640,029 Blair et al. May 26, 1953 2,646,399 Hughes July 21, 1953

1. FUEL OIL NORMALLY SUSCEPTIBLE TO SEDIMENT FORMATION IN STORAGECONTAINING A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ABIS-TETRAHYDROPYRIMIDINE JOINED AT THE 2-POSITION THROUGH A DIVALENTHYDROCARBON RADICAL AND THE AMIDES, SALTS AND ACID SALTS OF SAIDBIS-TETRAHYDROPYRIMIDINE, SAID COMPOUND HAVING THE PROPERTY OF AND BEINGPRESENT IN SUFFICIENT AMOUNT TO RETARD SAID SEDIMENT FORMATION.